If a program modifies more than one byte with one program instruction or statement, which is normally the case when storing a word, TotalView triggers the watchpoint with the lowest memory location in the modified region. Although the program might be modifying locations monitored by other watchpoints, TotalView only triggers the watchpoint for the lowest memory location. This can occur when your watchpoints are monitoring adjacent memory locations and a single store instruction modifies these locations.

For example, suppose that you have two 1-byte watchpoints, one on location 0x10000 and the other on location 0x10001. Also suppose that your program uses a single instruction to store a 2-byte value at locations 0x10000 and 0x10001. If the 2-byte storage operation modifies both bytes, the watchpoint for location 0x10000 triggers. The watchpoint for location 0x10001 does not trigger.

Here’s a second example. Suppose that you have a 4-byte integer that uses storage locations 0x10000 through 0x10003, and you set a watchpoint on this integer. If a process modifies location 0x10002, TotalView triggers the watchpoint. Now suppose that you’re watching two adjacent 4-byte integers that are stored in locations 0x10000 through 0x10007. If a process writes to locations 0x10003 and 0x10004 (that is, one byte in each), TotalView triggers the watchpoint associated with location 0x10003. The watchpoint associated with location 0x10004 does not trigger.